The present invention relates to a resistance heater made from a material such as graphite, SiC, etc., and more particularly to a heater to be used for directly or indirectly heating a semiconductor wafer in a semiconductor wafer processing device in which, for example, CVD (chemical vapor deposition) or other coating method is carried out.
An example of the prior art heaters is disclosed in Japanese patent publication No. 2005-86117(A). This heater uses an elongated ceramic body of a rectangular cross-section having greater width than thickness, which is formed into a ring or spiral configuration. This heater has low electric resistance, so that it will be required to use a power source that operates with low voltage and high current, resulting in increase of costs for the power source. In addition, this heater will tend to be bent, warped or deformed especially when it is subjected to a high temperature condition. This makes it impossible to uniformly heat a wafer or any other object to be processed at high temperature.
A typical shape of the prior art heater is shown in FIG. 3 herein, which includes an expanded view of terminal end portion with a connecting hole. The reason the terminal end portions have a widened and expanded shape at the end portion is that there needs to be decreased electric resistance at that portion so as to prevent that portion from over-heating. However, when using this heater, the expanded terminal end portion could make designing a heat pattern more difficult. A simple heat pattern could not be achieved with the prior art heater having the expanded terminal end portions.